Thrombocytopenia
Too few platelets, the blood cells that form clots, caused by chemotherapy or by the cancer in the marrow. Mild cases cause bruising; severe cases (under 10-20 × 10⁹/L) risk serious bleeding and need platelet transfusions.
Overview
Common with carboplatin, gemcitabine, temozolomide, lurbinectedin, PARP inhibitors (niraparib especially), radioligand therapies and in leukaemia and myeloma; it limits dose more often than neutropenia for some regimens because no growth factor is routinely used (romiplostim and avatrombopag are being trialled). Grade 4 is <25 × 10⁹/L. It also complicates anticoagulation for cancer-associated thrombosis and procedures such as biopsies and central line placement. Cirrhosis with portal hypertension causes chronic thrombocytopenia that constrains liver cancer treatment, and immune thrombocytopenia is an immune-related adverse event of checkpoint inhibitors.